After their testimony, Mr Trump said conditions at the centre had had “great reviews”. He then posted his series of tweets about the women and Ms Omar, attacks he redoubled on Monday.

“If you are not happy, if you are complaining all the time, you can leave,” he told a heated news conference outside the White House.

How have Democrats and Republicans responded?

Democrats have roundly condemned the president, and many were quick to say it was a racist attack.

However, top Republicans have been less outspoken. Senate Majority Leader Mitch McConnell said he would answer questions on Tuesday.

Treasury Secretary Steven Mnuchin said: “I don’t find them racist, the president just went on and clarified his comments.” He then changed the subject.

Some, including Senator Lindsey Graham, turned the topic back on to the politics of the four women, who are seen to be progressive. He told Fox News they are communists and anti-America.

US Senator and former presidential candidate Mitt Romney called Mr Trump’s remarks “destructive, demeaning, and disunifying”. But when a reporter asked him if they were racist, he walked away.

Lower-ranking members of the Republican Party were, however, more direct.

Tim Scott, the only African-American Republican in the Senate, called the president’s words “racially offensive”. Republican Congressman Will Hurd, who is also African American, described the comments as “racist and xenophobic”.

Democratic House Speaker Nancy Pelosi has, meanwhile, announced a resolution in the House to condemn the attack. She has urged Republicans to back it.